1. Field of the Invention
The present invention relates to an improvement in an air intake device for an engine in a watercraft.
2. Description of Background Art
Conventionally known is an air intake structure for an engine in a compact water gliding boat having a boat body in which the engine is provided and an air cleaner located on the rear side of the engine (see for example Japanese Patent Laid-Open No. 2004-52681 (FIGS. 3 and 4)).
FIG. 3 in Japanese Patent Laid-Open No. 2004-52681 is a schematic view of an engine E as viewed from the right side of a compact water gliding boat (reference characters or numerals cited herein are those shown in this publication). The engine E has a cylinder block 12 and a crankcase 13 provided on the lower side of the cylinder block 12. A collector box 5 for temporarily storing the air fed from an air cleaner box 3 (see FIG. 4) and supplying the air to an intake pipe 6 is provided on one side of the crankcase 13.
FIG. 4 in Japanese Patent Laid-Open No. 2004-52681 is a plan view of the engine E shown in FIG. 3. The engine E includes the air cleaner box 3 having an outside air inlet member 31, located on the rear side of the cylinder block 12, a throttle body 4 located on the front side of the air cleaner box 3, and the collector box 5 located on the front side of the throttle body 4. The engine E further includes the intake pipe 6 provided so as to connect the collector box 5 and the engine E, and a fuel injection valve 61 mounted on the intake pipe 6.
The air introduced from the outside air inlet member 31 is supplied through the air cleaner box 3 and the throttle body 4 to the collector box 5. Thereafter, the air is supplied through the intake pipe 6, in which the air is mixed with a predetermined amount of fuel injected by the fuel injection valve 61 to form an air-fuel mixture, which is then supplied to the engine E.
However, the outside air inlet member 31 is located in the air cleaner box 3, so that the length of an air intake duct is short. Accordingly, there is little room of controlling the length of the air intake duct, and the flow of air in the air intake duct cannot be sufficiently straightened. Further, since the length of the air intake duct is short, noise from the engine easily leaks through the air intake duct.
Further, since the outside air inlet member 31 is located on the rear side of the cylinder block 12, the outside air inlet member 31 introduces the air passed along the side surface of the engine and therefore warmed by the heat from the engine. The higher the temperature of an intake air, the lower the intake efficiency of the engine, causing an adverse effect on the output from the engine.